Modified sampling and analysis method for large volatility range airborne polycyclic aromatic hydrocarbons (PAH) using gas chromatography-mass spectrometry

A sampling method has been developed for the measurement for polycyclic aromatic hydrocarbons in ambient air by gas chromatography isotope dilution mass spectrometry. The method has been designed to measure the largest possible volatility range of PAHs including the abundant naphthalenes. Sample volumes were approx. 500 m³ in size at a sampling rate of approx. 18 m³/h. The sampler contained three sorption stages for the simultaneous capturing of particle bound and low and high volatile gaseous PAH, respectivley. Recoveries of sampling spikes were on average 90%. The detection limit was approx. 5 pg/m³ for the high boiling range PAH. Results obtained showed a quite steady profile for most PAH in background air in The Netherlands. Comparison of abundance ratios with literature data indicate that traffic exhausts are the major source for the PAH in the area.     

Further studies on dppm-stabilized mixed-metal clusters: X-ray structure of PdPtCoCl(CO)3(μ-dppm)2 1

The metalloligated mixed-metal cluster [PdPtCo₂(CO)₇(-dppm)₂] (2) (dppm = -Ph₂PCH₂PPh₂) possesses numerous potential reaction centers (e.g., metal(s), metal-metal bonds, CO, and dppm ligands) and this has previously led to an investigation of the site selectivity of reactions with nucleophiles. The exocyclic CO(CO)₄ fragment was substituted with a chloride ligand and the resulting chiral, triangular cluster PdPtCoCl(CO)₃(-dppm)₂ (4) has been structurally characterized. The Pd-Co and Pt-Co edges of this almost equilateral triangle are bridged by a dppm ligand, and two of the three carbonyls borne by the Co atom are semi-triply bridging above and below the plane of the metals. The Co(CO)₃P fragment behaves as an anionic 4-electron donor organometallic bridging group toward thed ⁹-d ⁹ Pd(I)-Pt(I) unit. Crystal data for4, monoclinic space groupP2₁/n with Z=4 in a unit cell of dimensionsa=12.291(3),b=19.321(4),c=23.680(5) Å,=100.05(2)°. The structure has been solved from diffractometer data by Patterson, Fourier methods and refined by full-matrix least squares on the basis of 3512 observed reflections (l>3) toR(F) andR _w(F) values of 0.059 and 0.061.Dedicated to Professor L. F. Dahl on the occasion of his 65th birthday, with our sincere congratulations and best wishes.     

PROFLAVINE MEDIATED PHOTOINACTIVATION OFBACTERIOPHAGE φX174 AND ITS ISOLATED DNA: EFFECTS OF AGENTS MODIFYING VARIOUS PHOTOCHEMICAL PATHWAYS

Abstract. Thiols and disulfides protect both φX174 phage and its isolated DNA from the lethal action of proflavine plus light. The protective ability of these compounds appears to be attributed to the -SH or the -S-S- group and the property to interact with the proflavine-phage DNA complex. The phage inactivation efficiency per proflavine bound to DNA is reduced by 50 to 30% upon addition of cysteine or cystamine. Substances that affect the lifetime of singlet oxygen modify the rate of phage photoinactivation in the presence of proflavine; the inactivation rate is decreased by N^-₃ and increased by D₂O. Irradiation under N₂ atmosphere markedly decreases the phage photosensitization by proflavine. Irradiation with monochromatic light of 440 nm is less efficient than irradiation with light of 440 nm plus 360 nm, and the difference is more pronounced in N₂ than in air. These results are discussed in relation to various possible photochemical pathways.     

Automated chemical separations in routine activation analysis

In recent years increased information is required about the distribution of elements at low concentration levels in the biosphere. Neutron activation analysis can play an important role if it can supply many data at relatively low cost. As some of the concentrations are too low for determination by non-destructive techniques, equipment for chemical separations on a routine basis is necessary. For environmental studies a separation scheme has been developed successfully for arsenic, antimony, cadmium, copper, mercury, selenium and zinc. It is based on a combination of distillation and ion-exchange. Special attention is paid to the prevention of interference from bromine and sodium. Additional information about chromium, cobalt, nickel and tungsten can easily be obtained. Experience gathered with an automated instrument for fifty samples a week is described.     

Cytotoxicity and Antiproliferative Effect of Hypericin and Derivatives after Photosensitization

The toxicity on three human tumor cell lines (A431, HeLa and MCF7) of five phenanthroperylenequinones (hypericin and derivatives) and two perylenequinones (cercosporin and calphostin C) was investigated after photosensitization (4 J/cm²). Furthermore, the antiproliferative effect on HeLa cells was studied for the phenanthroperylenequinones. Hypericin, 2,5-dibromohypericin, 2,5,9,12-tetrabromohypericin and perylenequinones displayed a potent cytotoxic and antiproliferative effect in the nanomolar range. Hypericin dicarboxylic acid exhibited no photoactivity. In general, the antiproliferative activity correlated well with the photocytotoxicity. However, the nonphotocytotoxic compound hexamethylhypericin showed potent antiproliferative activity in the nanomolar range, probably exerting its action by protein kinase C inhibition. Without light irradiation, no cytotoxic and antiproliferative effect was observed for any photocytotoxic phenanthroperylenequinone compound. Furthermore, confocal laser microscopy revealed that the subcellular localization in A431 cells was similar for the photoactive compounds; the photosensitizers were mainly concentrated in the perinuclear region, probably corresponding with the Golgi apparatus and the endoplasmic reticulum. In addition, the accumulation of the photosensitizers in HeLa cells was investigated. All compounds except hypericin dicarboxylic acid were found to concentrate to a large extent in the cells. The compound 2,5,9,12-tetrabromohypericin seemed intrinsically more effective than hypericin since the intracellular concentration of the bromoderivative was a magnitude of order lower than that of hypericin although both compounds showed similar photobiological activity.     

Extraction and exchange behavior of metal species in therapeutically applied peat

The binding and availability of metals (Al, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Zn) in therapeutically applied peat (Grosses Gifhorner Moor, Sassenburg/North Germany) was characterized by means of a versatile extraction approach. Aqueous extracts of peat were obtained by a standardized batch equilibrium procedure using high-purity water (pH 4.5 and 5.0), 0.01 mol l(-1) calcium chloride solution, 0.01 mol l(-1) ethylenediaminetetraacetic acid (EDTA) and 0.01 mol l(-1) diethylenetriamine pentaacetic acid (DTPA) solution as metal extractants. In addition, the availability of peat-bound metal species was kinetically studied by collecting aliquots of extracts after different periods of extraction time (5, 10, 15, 30, 60 and 120 min). Metal determinations were performed by atomic spectrometry methods (AAS, ICP-OES) and dissolved organic matter (DOM) was characterized by UV/Vis measurements at 254 and 436 nm, respectively. Of the extractants studied Ca, Mg and Mn were the most available metals, in contrast to peat-bound Fe and Al. The relative standard deviation s(r) of the developed extraction procedures was mostly in the range of 4 to 20%, depending on the metal and its concentration in peat. A pH increase favored the extraction of metals and DOM from peat revealing complex extraction kinetics. Moreover, a competitive exchange between peat-bound metal species and added Cu(II) ions showed that >100 mg of Cu(II) per 50 g wet peat was necessary to exchange the maximum of bound metals (e.g. 21.8% of Al, 3.9% of Fe, 79.0% of Mn, 81.9% of Sr, related to their total content).     

Thermodynamic evidence for Ca2+-mediated self-aggregation of Lewis X gold glyconanoparticles. A model for cell adhesion via carbohydrate-carbohydrate interaction

Thermodynamic evidence for the selective Ca(2+)-mediated self-aggregation via carbohydrate-carbohydrate interactions of gold glyconanoparticles functionalized with the disaccharides lactose (lacto-Au) and maltose (malto-Au), or the biologically relevant trisaccharide Lewis X (Le(X)-Au), was obtained by isothermal titration calorimetry. The aggregation process was also directly visualized by atomic force microscopy. It was shown in the case of the trisaccharide Lewis X that the Ca(2+)-mediated aggregation is a slow process that takes place with a decrease in enthalpy of 160 +/- 30 kcal mol(-)(1), while the heat evolved in the case of lactose and maltose glyconanoparticles was very low and thermal equilibrium was quickly achieved. Measurements in the presence of Mg(2+) and Na(+) cations confirm the selectivity for Ca(2+) of Le(X)-Au glyconanoparticles. The relevance of this result to cell-cell adhesion process mediated by carbohydrate-carbohydrate interactions is discussed.     

Mass spectrometric characterization of two novel inflammatory peptides from the venom of the social wasp Polybia paulista

The social wasp P. paulista is relatively common in southeast Brazil causing many medically important stinging incidents. The seriousness of these incidents is dependent on the amount of venom inoculated by the wasps into the victims, and the characteristic envenomation symptoms are strongly dependent on the types of peptides present in the venom. In order to identify some of these naturally occurring peptides available in very low amounts, an analytical protocol was developed that uses a combination of reversed-phase and normal-phase high-performance liquid chromatography (HPLC) of wasp venom for peptide purification, with matrix-assisted laser desorption/ionization time-of-flight post-source decay mass spectrometry (MALDI-Tof-PSD-MS) and low-energy collision-induced dissociation (CID) in a quadrupole time-of-flight tandem mass spectrometry (QTof-MS/MS) instrument for peptide sequencing at the sub-picomole level. The distinction between Leu and Ile was achieved both by observing d-type fragment ions obtained under CID conditions and by comparison of retention times of the natural peptides and their synthetic counterparts (with different combinations of I and/or L at N- and C-terminal positions). To distinguish the isobaric residues K and Q, acetylation of peptides was followed by Q-Tof-MS analysis. The primary sequences obtained were INWLKLGKMVIDAL-NH(2) (MW 1611.98 Da) and IDWLKLGKMVMDVL-NH(2) (MW 1658.98 Da). Micro-scale bioassay protocols characterized both peptides as presenting potent hemolytic action, mast cell degranulation, and chemotaxis of polymorphonucleated leukocyte (PMNL) cells. The primary sequences and the bioassay results suggest that these toxins constitute members of a new sub-class of mastoparan toxins, directly involved in the occurrence of inflammatory processes after wasp stinging.     

Detection of soil pollution by hydrocarbons using headspace-mass spectrometry and identification of compounds by headspace-fast gas chromatography-mass spectrometry

The direct coupling of a headspace sampler with a mass spectrometer is proposed as a screening tool for the rapid detection of soil pollution by hydrocarbons from petroleum and derivatives. The samples are subjected to the headspace generation process, with no prior treatment, and the volatiles generated are introduced directly into the mass spectrometer, thereby obtaining a fingerprint of the sample analysed. Suitable treatment of the signal by chemometric techniques allows unequivocal characterisation of the different types of sample. The use of fast gas chromatography with a mass spectrometer detector coupled to the headspace sampler allows identification of the major hydrocarbons present in the mineral and organic polluted samples, interpretation of the results obtained, and demonstrates the analytical potential of headspace-mass spectrometry coupling.     

The role of hydrogen bonding in supercooled methanol

The role of hydrogen bonding on the microscopic properties of supercooled methanol has been analyzed by means of molecular dynamics simulations. Thermodynamic, structural, and dynamical properties have been investigated in supercooled methanol. The results have been compared with those of an ideal methanol-like system whose molecules have the same dipole moment as the methanol but lack sites for hydrogen bonding. Upon cooling the methanol samples, translational relaxation times increase more rapidly than reorientational ones. This effect is much more important when hydrogen bonds are suppressed. Suppression of hydrogen bonds also results in lower critical temperatures for diffusion and for several characteristic relaxation time constants. The anisotropy of individual dynamics and the existence of dynamical heterogeneities have also been investigated.